Recticel Eurowall® Partial Fill Cavity Insulation Board

Recticel Eurowall® Partial Fill Cavity Insulation Board Review

Recticel Eurowall® Cavity is the board you reach for when the wall is designed around a clear cavity rather than a filled one. It is not trying to pack the whole cavity out. It is built to sit against the inner leaf and leave a residual cavity in front of it.

That single design decision shapes everything about the board. Partial fill insulation has to hold its position against the inner leaf, keep a clean clear cavity behind the outer leaf, and pull its weight thermally without relying on filling the gap. Recticel Eurowall® Cavity is a PIR board faced on both sides with a gas-tight, low-emissivity foil, and that foil is doing real work in this build-up rather than just protecting the foam.

For new masonry walls, extensions and commercial units where the specification calls for a partial fill cavity with a maintained clear gap, this is the board to look at.

The Recticel Eurowall® Cavity range at a glance

Insulation UK stocks the Eurowall® Cavity range from 50mm up to 100mm, all in a 1200mm x 450mm board. Every thickness shares the same 0.022 W/mK thermal conductivity, so the R-value steps up cleanly as the board gets thicker.

R-values are taken from the Recticel Eurowall Cavity technical datasheet.

Recticel Eurowall® Cavity value

The value here is not just the lambda figure. A lot of PIR boards land at 0.022 W/mK. What makes Eurowall® Cavity a partial-fill product rather than a generic board is the low-emissivity foil facing on both faces.

In a partial fill wall there is a clear cavity sitting in front of the insulation. The low-emissivity facing reduces radiant heat transfer across that clear gap, which adds to the thermal performance of the wall on top of the board's own resistance. That reflective contribution is only counted in the wall calculation when the residual cavity is non-ventilated, so it is worth confirming the cavity detail against the build-up before relying on it.

For trade buyers, that means a board specified for the way partial fill walls actually work. For self-builders and homeowners, it means you are buying a board designed for a clear-cavity wall rather than one squeezed into the wrong method.

Thermal performance

Recticel Eurowall® Cavity has a declared thermal conductivity of 0.022 W/mK across every thickness, which puts it in high-performance PIR territory. The R-values rise steadily through the range, from 2.25 m²K/W at 50mm to 4.50 m²K/W at 100mm.

The thicker the board, the higher its thermal resistance. The trade-off in partial fill is cavity width. Because a clear residual cavity has to be kept in front of the board, a thicker board needs a wider overall masonry cavity to fit. That is the balance to work through when choosing a thickness, rather than just chasing the highest number.

It is worth being accurate here: the board does not set the finished wall U-value on its own. The final U-value depends on the full construction, including block type, cavity width, the clear cavity detail, wall ties, mortar joints, internal finishes and the quality of installation.

Installation and site practicality

Eurowall® Cavity has straight edges on all four sides and a grid pattern printed on the facing, which gives a clean reference for cutting and helps boards butt together with minimal gaps. It is fixed back against the inner leaf and held in place with wall ties and retaining clips as the inner leaf is built, with the clear cavity kept open in front.

The 1200mm x 450mm board is sized to course in with standard blockwork, which keeps cutting down on a typical run. Keeping the clear cavity clean during the build matters as much as the board itself, since the residual gap is part of how the wall handles moisture.

Wind-driven rain and wall performance

This is where the partial fill principle earns its place. The clear residual cavity is the wall's main line of defence against wind-driven rain. Any water that gets through the outer leaf runs down the cavity face of the brickwork and drains out, rather than tracking across to the inner leaf.

Eurowall® Cavity supports this by being moisture resistant and by keeping its position against the inner leaf, so the clear cavity stays clear. It does not remove the need for correct wall design, exposure-zone assessment, cavity trays, weep holes, wall ties and good workmanship. Those still carry the rain-resistance job. The board is designed to work with that detailing, not replace it.

Which thickness should you choose?

Quality and specification confidence

Recticel Eurowall® Cavity is BBA certified (certificate 02/3908, covering 20 to 160mm, so all six stocked thicknesses fall within scope) and manufactured to EN 13165 under ISO 9001 and ISO 14001. The foam is PEFC certified, and a technical datasheet is available for the range.

That paperwork matters on a partial fill wall, where building control, architects and energy assessors will want to see declared performance and certification behind the board. Eurowall® Cavity gives you that supporting documentation to put in front of them.

Any drawbacks?

The main thing to be clear about is that this is a specification-led board, not a buy-it-and-go product. You need to confirm the cavity width, the required clear cavity, the target U-value, the exposure zone and the wall type before settling on a thickness. The reflective benefit of the foil facing only counts where the cavity is non-ventilated, which is another detail to check rather than assume.

The boards also carry a Euroclass F reaction-to-fire classification, which needs to be considered as part of the wider wall design, particularly on projects with stricter fire requirements or where additional restrictions apply.

Our expert verdict

Recticel Eurowall® Cavity is a strong choice in the partial fill cavity category for one clear reason: it is built for the clear-cavity method rather than borrowed from a full fill board. The 0.022 W/mK conductivity gives it a high-performance base, the low-emissivity foil facing adds a real reflective contribution across the clear cavity, and the straight-edged board sits cleanly against the inner leaf.

If you want a common all-round partial fill spec, the 75mm board is the natural starting point. Where the cavity is tight, the 50mm and 60mm boards keep the same board design in a slimmer format. Where the wall is designed wider and performance is the priority, the 90mm and 100mm boards are the clear upgrades.

For new masonry walls built on a partial fill, clear-cavity design, Recticel Eurowall® Cavity is a strong range to have on the shortlist.